Magnetism of Amorphous Metals and Alloys

Abstract

The last chapter is devoted to the magnetism of amorphous metals and alloys. We describe here the theories of amorphous metallic magnetism. Some of the amorphous magnetic alloys showing strong ferromagnetism are explained by a generalization of the Slater–Pauling curve picture, while the other amorphous alloys close to the amorphous pure metals show anomalous magnetic behaviors such as the emergence of the spin glass due to the structural disorder, the enhancement of the Curie temperatures, and the change from the strong ferromagnet to a weak ferromagnet. The amorphous metallic magnetism has to be clarified from a viewpoint of the structure vs. magnetism. We first overview how to construct the amorphous structure of the alloys. Next, we present a method to calculate the electronic structure of amorphous alloys with use of the tight-binding (TB) LMTO method and the recursion method. On the basis of the calculated electronic structure, we construct a finite-temperature theory of the local environment effects (LEE) for amorphous metals and alloys. We explain the anomalous behaviors of the magnetism in various amorphous alloys at the ground state using the TB-LMTO recursion method, and their magnetism at finite temperatures using the finite-temperature theory of the LEE.